1. Field of the Invention
The present invention relates to a system that connects an optical head to additional electronics in an optical drive.
2. Description of Related Art
A conventional optical drive (e.g., a compact disk player) typically includes a stationary optical unit, a movable optical unit, and an actuator. The stationary optical unit generally includes a laser diode, a half mirror, and a photodetector. The laser diode generates a light beam that is reflected by the half mirror onto the movable optical unit. The movable optical unit typically includes an objective lens that focuses the light beam on a spinning optical disk.
The actuator aligns the movable optical unit with the tracks of the optical disk so that the light beam reflects off the lands and pits of the tracks. The reflected light beam travels back through the movable optical unit and back to the stationary optical unit. The light beam is transmitted through the half mirror onto the photodetector where the varying intensity of the light is changed to electrical signals.
Optical drives are becoming smaller so they can be integrated into portable devices including laptop computers and personal digital assistants (PDAs). Close arrangement and integration of components help to miniaturize optical drives. For example, the stationary and movable optical units described above can be integrated into a single component (an integrated optical head) called xe2x80x9coptical pickup unitxe2x80x9d or xe2x80x9cOPUxe2x80x9d. An actuator arm can then be used to place the OPU over the tracks of a spinning medium.
FIG. 1 illustrates an assembly 10 used to connect an OPU 20 to a printed circuit board 60 (or electronics of an optical drive). OPU 20 is mounted atop a copper plate 30 through a cutout of a fiberglass layer 40. Fiberglass layer 40 includes pad 42, pad 44, and trace 46. Pad 42 of fiberglass layer 40 is coupled to pad 22 of OPU 20 via a bond wire 25. Plate 30 is mounted atop a flexible circuit 50 (or vice versa). Flexible circuit 50 includes pad 52, trace 54, and a connector 56. Pad 44 of fiberglass layer 40 is coupled to pad 52 of flexible circuit 50 via a solder joint 35. Flexible circuit 50 is next coupled to a printed circuit board 60 via connector 56.
Assembly 10 has several disadvantages. Each of the wire bonds and solder joints in assembly 10 forms a point of failure that may break during use. Thus, the many wire bonds and solder joints in assembly 10 create multiple points of failure. Each of the wire bonds and solder joints must be formed during fabrication. Thus, the many wire bonds and solder joints increase fabrication cost. Solder joints also require large pads, thereby increasing the overall size of the fiberglass and flexible circuit layers. Assembly 10 is also constructed from multiple layers of silicon, fiberglass, copper, and flex circuit that increase the overall weight and volume of the optical drive. Accordingly, there is a need for a method and a system to connect the OPU to the remaining electronics of the optical drive while improving reliability and minimizing weight and volume.
An optical assembly includes an optical head, an actuator an for positioning the optical head, and a flex circuit for carrying signals from the optical head. The flex circuit is coupled to the optical head by at least one wire. In one embodiment, the flex circuit carries signals from the optical head to a printed circuit board. In one implementation, the flex circuit also carries signals from the printed circuit to the optical head.
In one embodiment, the optical head is mounted atop a plate, the plate is mounted atop the flex circuit, and the wire couples a pad on the flex circuit to a pad on the optical head through a cutout in the plate. In another embodiment, the flex circuit is mounted atop a plate and the optical head is mounted atop the plate. In one implementation, the optical head is mounted atop the plate through a cutout of the flex circuit.
The optical assembly described above eliminates the use of an intermediate fiberglass layer, thereby improving reliability by reducing the number of wire bonds and conserving weigh and volume of the optical assembly.